JiangHua Zhu created HDFS-16594:
-----------------------------------
Summary: Many RpcCalls are blocked for a while while Decommission
works
Key: HDFS-16594
URL: https://issues.apache.org/jira/browse/HDFS-16594
Project: Hadoop HDFS
Issue Type: Improvement
Components: namenode
Affects Versions: 2.9.2
Reporter: JiangHua Zhu
Attachments: image-2022-05-26-02-05-38-878.png
When there are some DataNodes that need to go offline, Decommission starts to
work, and periodically checks the number of blocks remaining to be processed.
By default, when checking more than
50w(${dfs.namenode.decommission.blocks.per.interval}) blocks, the
DatanodeAdminDefaultMonitor thread will sleep for a while before continuing.
If the number of blocks to be checked is very large, for example, the number of
replicas managed by the DataNode reaches 90w or even 100w, during this period,
the DatanodeAdminDefaultMonitor will continue to hold the FSNamesystemLock,
which will block a lot of RpcCalls. Here are some logs:
!image-2022-05-26-02-05-38-878.png!
It can be seen that in the last inspection process, there were more than 100w
blocks.
When the check is over, FSNamesystemLock is released and RpcCall starts working:
'
2022-05-25 13:46:09,712 [4831384907] - WARN [IPC Server handler 36 on
8021:Server@494] - Slow RPC : sendHeartbeat took 3488 milliseconds to process
from client Call#5571549 Retry#0
org.apache.hadoop.hdfs.server.protocol.DatanodeProtocol.sendHeartbeat from
10.196.145.92:35727
2022-05-25 13:46:09,712 [4831384907] - WARN [IPC Server handler 135 on
8021:Server@494] - Slow RPC : sendHeartbeat took 3472 milliseconds to process
from client Call#36795561 Retry#0
org.apache.hadoop.hdfs.server.protocol.DatanodeProtocol.sendHeartbeat from
10.196.99.152:37793
2022-05-25 13:46:09,712 [4831384907] - WARN [IPC Server handler 108 on
8021:Server@494] - Slow RPC : sendHeartbeat took 3445 milliseconds to process
from client Call#5497586 Retry#0
org.apache.hadoop.hdfs.server.protocol.DatanodeProtocol.sendHeartbeat from
10.196.146.56:23475
'
'
2022-05-25 13:46:09,712 [4831384907] - WARN [IPC Server handler 33 on
8021:Server@494] - Slow RPC : sendHeartbeat took 3435 milliseconds to process
from client Call#6043903 Retry#0
org.apache.hadoop.hdfs.server.protocol.DatanodeProtocol.sendHeartbeat from
10.196.82.106:34746
2022-05-25 13:46:09,712 [4831384907] - WARN [IPC Server handler 139 on
8021:Server@494] - Slow RPC : sendHeartbeat took 3436 milliseconds to process
from client Call#274471 Retry#0
org.apache.hadoop.hdfs.server.protocol.DatanodeProtocol.sendHeartbeat from
10.196.149.175:46419
2022-05-25 13:46:09,712 [4831384907] - WARN [IPC Server handler 77 on
8021:Server@494] - Slow RPC : sendHeartbeat took 3436 milliseconds to process
from client Call#73375524 Retry#0
org.apache.hadoop.hdfs.server.protocol.DatanodeProtocol.sendHeartbeat from
10.196.81.46:34241
'
Since RpcCall is waiting for a long time, RpcQueueTime+RpcProcessingTime will
be longer than usual. A very large number of RpcCalls were affected during this
time.
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